So can we presume the DDEC II got a taste of 24v ? or did the clock battery go dead from setting so long without power

It never set a code and it was still readable but when the guy put the battery on backwards he spiked the ECM , I had it rebuilt and she fired up, but I have a world of illness with this one, the spike also get the alternator, I am replacing it and going one step at a time in replacing stuff the spike got.

DDEC II can be upgraded to DDEC III, no DDECIV available for a coach 8V92. The down side is DDECIII inability to comunicate with the ATEC1 (CEC) transmission controls.The right way to upgrade is to upgrade the transmssion to a WTECIII controlled HD 6 speed and the engine to a DDECIII, which will comunicate and give you optimum performance.Just completed one, results where awesome!

What does it take to upgrade an 8V92TA DDEC II to a DDEC III? When I had to replace my DDEC II ECM last summer I asked about an upgrade and was told by Interstate Detroit Diesel in Sioux Falls, SD that it couldn't be done. Then again at Interstate Detroit Diesel in Fargo, ND I was told the same thing. How did you do it? I have an Allison 740 transmission so no electronics there.

I don't want to upgrade now, but as long as I had to replace my ECM last summer anyway, that is when it would have been practical to upgrade. But, I was told twice that I couldn't. That is why I asked how Electman did it. From reading another post of his, I think he upgraded by changing both the engine and transmission as a package. I hope he responds to my question so I can know for sure.

Sam,,unless you have a real early version of the DDEC 11 they are not that hard to upgrade to a 111 or IV, early versions of the 11 require a cam change because unlike a 60 series there is no bull gear you can change like on the early 60 series then it gets costly.

All I have been around just takes the new harness's,programing,a couple extra sensors and a new crankshaft positioning sensor , is yours a Motorola ECM ? The 111 is faster and has more memory than a 11 but that is no asset for you using a 740

I am not interested in changing from DDEC II to anything else at this time. My original 1990 ECM was a version 111 my current ECM is version 154. My fuel milage dropped dramatically after the ECM change, but that is also when my engine started smoking badly. The smoking problem was from a blown exhaust manifold gasket, that has been fixed. I also cut a hole in the side of the bus above the air cleaner intake to allow the engine to breath better. It will be interesting to see if the fuel mileage goes back to the previous level after I drive the bus enough to use a few tanks of fuel.